1. Technical Field
The present disclosure relates to strain measurement devices and methods for measuring strain and, particularly, to a strain measurement device based on carbon nanotubes and a method for measuring strain using the same.
2. Description of Related Art
Strain is an amount of deformation of a body due to an applied force. More specifically, strain (ε) is defined as the fractional change in length, and can be positive (tensile) or negative (compressive). In practice, the magnitude of measured strain is very small.
While there are several methods of measuring strain the most common is with a strain gage, a device whose electrical resistance varies in proportion to the amount of strain in the device. The most widely used gage is a bonded metallic strain gage.
The metallic strain gage consists of a very fine wire or, more commonly, metallic foil arranged in a grid pattern. The grid pattern maximizes the amount of metallic wire or foil subject to strain in the parallel direction. The cross-sectional area of the grid is minimized to reduce the effect of shear strain and Poisson Strain. The grid is bonded to a thin backing, called the carrier, which is attached directly to the test specimen. Therefore, the strain experienced by the test specimen is transferred directly to the strain gage, which responds with a linear change in electrical resistance. In application, a voltage is applied on the strain gage, and a circuit system is used to measure the change of electrical resistance, and output the strain.
However, the electrical resistance change of the metallic strain gage is not sensitive to the small strain; therefore, it can not measure the small strain of the specimen when a force is applied on it.
What is needed, therefore, is to provide a strain measurement device can measure the small strain, and a method using the same.